Volume is the number that actually moves

Single sessions lie. Sleep, caffeine, whether the bar felt light today — one workout tells you almost nothing about whether your training works. Weekly volume per muscle group is the number that behaves: it responds to planning, it predicts growth about as well as anything we can measure, and you control it completely.

The catch: everyone says “track your volume” and almost nobody agrees on what to count. This post is the counting rules.

Two definitions, two jobs

Hard sets per muscle per week. A set taken close to failure counts as 1, whether it’s 60 kg or 120 kg. This is the planning currency: program design, “is my back getting enough,” comparing this week to last week.

Tonnage — weight × reps, summed. This is the trend currency. It catches the slow drift when your set count stays at 12 but the bar keeps getting heavier. It’s useless for comparing muscle groups against each other (leg tonnage dwarfs arm tonnage forever) but good for watching one group over months.

Use sets to plan, tonnage to trend. Don’t mix the jobs.

Here’s the honest split with Repsheet: it gives you the tonnage side automatically — volume by muscle group over the last 30 days, an 8-week total-volume chart, and a body heatmap that shades that same per-muscle tonnage onto a silhouette. Hard-set counting is the part you do by hand when planning; the app tracks kg, not weekly hard sets.

What counts as one set

A working set: your prescribed weight, taken within a few reps of failure. That’s the unit.

Warm-ups don’t count. Two easy sets with the empty bar are joint prep, not stimulus. Since Repsheet builds PRs from the sets you tick complete, keep them out the simple way — don’t mark your warm-ups complete.
Drop sets: the common rule is to count the whole sequence as 1, maybe 2. Pick one rule and stop thinking about it.
A set you abandoned at 3 reps because your grip died: doesn’t count. It didn’t do the job.

One honest caveat about the app’s math: the kg totals sum every set you tick complete — so if you do mark warm-ups done, they land in your tonnage too. The noise from a couple of empty-bar sets is small, but it’s there. For planning decisions, count your working sets yourself; the app tracks kg, it doesn’t separate hard sets from warm-ups.

How many sets per week

The research answer, hedged the amount it deserves: most reviews land around 10–20 hard sets per muscle per week for growth in people who’ve been training a while. Ten is a solid default. Below roughly 4–6 you’re maintaining, not building. Above 20 the returns flatten while the recovery bill keeps climbing — and the literature genuinely fights about that top end.

Beginners grow on less. If you’ve been lifting under a year, 8–10 sets per group is plenty, and adding more mostly adds soreness.

The useful move isn’t picking the perfect number. It’s noticing that your chest gets 16 sets a week and your hamstrings get 2 — and that you had no idea until you counted.

The indirect-volume problem

Rows work your biceps. Bench works your triceps and front delts. Do those count?

There are two defensible rules: count direct sets only, or count indirect work as half a set. The first is simpler and it’s the one Repsheet enforces by design — every exercise logs to one muscle group, so bench press lands on chest, not on chest plus shoulders plus arms.

The trade-off is real: if you press a lot, your triceps get more work than the “arms” number shows. Read a pale arms number with that in mind before you bolt on four sets of pushdowns.

What matters more than the rule is that it never changes. A counting rule that shifts week to week produces numbers you can’t compare, which is worse than no numbers.

The weekly check

Once a week, not daily — daily volume checks are noise-reading:

Open the stats screen. Look at volume by muscle group over the last 30 days.
Glance at the body heatmap. Anything unexpectedly pale?
If a group has been pale or absent two weeks running, add 3–4 direct sets to it next week. Don’t add anything to the groups that are already dark red.

And if every number has been climbing for a month while your working weights go nowhere — that’s not a volume problem. That’s a deload signal.

Count working sets, check weekly, change one thing at a time. That’s the whole discipline.